title: Ontogeny of vasoconstrictor neurohypophysial hormone function in rats.
abstract: This in vitro study examined the ontogeny of arginine vasopressin (AVP) and arginine vasotocin (AVT) compared with norepinephrine (NE)-mediated contraction in rat thoracic aortas. Aortas from three age groups (2-3 days, 6-7 days, and 12 wk) of Sprague-Dawley rats were used. Ring segment resting length was adjusted to optimize tension developed to a dose that produces half-maximal tension of NE in Krebs solution (pH 7.4, 37 degrees C) and gassed with 95% O2-5% CO2. Cumulative dose-response curves were generated for KCl (5-100 mM), NE (10(-10)-10(-5) M), AVP, and AVT (both 10(-10)-10(-6) M) in the presence and absence of a selective V1 vasopressinergic inhibitor, [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine]arginine vasopressin ([d(CH2)5Tyr(Me)]AVP). A progressive increase in sensitivity among all age groups was found for KCl and NE. There was a slight decrease in sensitivity to both AVP and AVT in the 1st wk. Maximum contractile response to NE increased between 2-3 and 6-7 days, whereas no change was observed for KCl, AVP, or AVT. AVP- and AVT-mediated contractions were selectively inhibited by [d(CH2)5Tyr(Me)]-AVP. These results suggest 1) receptor-mediated contractility is present from 2 days of age for NE, AVP, and AVT; 2) sensitivity to KCl and NE increases progressively during postnatal development, whereas sensitivity to AVP and AVT slightly decreases in the 1st wk with no progressive age-related increase by 12 wk; 3) AVP and AVT mediate contraction via a similar V1-like receptor.
authors.affiliation: Department of Pediatrics, Kapiolani Medical Center for Women and Children, John A. Burns School of Medicine, Honolulu 96826.
authors.forename: L K
authors.initials: LK
authors.lastname: Kullama
authors.forename: V
authors.initials: V
authors.lastname: Balaraman
authors.forename: J R
authors.initials: JR
authors.lastname: Claybaugh
authors.forename: W M
authors.initials: WM
authors.lastname: Ichimura
authors.forename: K T
authors.initials: KT
authors.lastname: Nakamura
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D010907:Pituitary Hormones / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014661:Vasoconstriction / Q000502:physiology*; D014667:Vasopressins / Q000037:antagonists & inhibitors; D014668:Vasotocin / Q000494:pharmacology
chemical_list: D010907:Pituitary Hormones; D014667:Vasopressins; D001127:Arginine Vasopressin; D011189:Potassium Chloride; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-; D014668:Vasotocin; D009638:Norepinephrine